Nonaqueous electrolyte battery, battery pack and positive electrode

ABSTRACT

According to one embodiment, there is provided a nonaqueous electrolyte battery including a positive electrode, a negative electrode, a nonaqueous electrolyte and a separator. The positive electrode includes a positive electrode active material containing Li x Ni 1−a−b Co a Mn b M c O 2  (0.9&lt;x≦1.25, 0&lt;a≦0.4, 0≦b≦0.45, 0≦c≦0.1, and M represents at least one element selected from the group consisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn). The separator includes polyester. A pore volume in a pore size distribution according to a mercury intrusion porosimetry is in a range of 0.9 cm 3 /g to 3 cm 3 /g. An air permeability value according to a Gurley method is in a range of 2 sec/100 ml to 15 sec/100 ml.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of PCT Application No.PCT/JP2015/080725, filed Oct. 30, 2015 and based upon and claiming thebenefit of priority from Japanese Patent Application No. 2014-223068,filed Oct. 31, 2014, the entire contents of all of which areincorporated herein by reference.

FIELD

Embodiments of the present invention relate to a nonaqueous electrolytebattery, a battery pack and a positive electrode.

BACKGROUND

Since polyester has a high melting point and high oxidation resistance,and further has low hydrophilicity, it is useful as a material of aseparator for a nonaqueous electrolyte battery. However, on the otherhand, a separator made of polyester hydrolyzes in a basic condition, andtherefore the separator has a defect that a battery resistance increasesdue to the hydrolysis of the separator when the separator is usedtogether with an active material containing a large amount of residualalkali components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a nonaqueous electrolytebattery according to an embodiment.

FIG. 2 is a partially developed perspective view of an electrode groupused in the nonaqueous electrolyte battery of FIG. 1.

FIG. 3 is a block diagram showing an electric circuit of a battery packaccording to an embodiment.

FIG. 4 is a view showing pore size distributions according to a mercuryintrusion porosimetry of separators used in Example A-1 and ComparativeExample A-1.

DETAILED DESCRIPTION

According to one embodiment, there is provided a nonaqueous electrolytebattery including a positive electrode, a negative electrode, aseparator and a nonaqueous electrolyte. The positive electrode includesa positive electrode active material containingLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn). The separator isdisposed between the positive electrode and the negative electrode. Theseparator includes polyester. A pore volume in a pore size distributionaccording to a mercury intrusion porosimetry of the separator is in arange of 0.9 cm³/g to 3 cm³/g. An air permeability value according to aGurley method of the separator is in a range of 2 sec/100 ml to 15sec/100 ml.

According to another embodiment, there is provided a battery packincluding the nonaqueous electrolyte battery according to theembodiment.

According to another embodiment, there is provided a positive electrodefor a battery to be used with a negative electrode and a separator. Thepositive electrode includes a current collector and a positive electrodeactive material. The positive electrode active material containsLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn).

Hereinafter, embodiments will be described with reference to thedrawings.

First Embodiment

The inventors found that life characteristics of a nonaqueouselectrolyte battery are improved by using a positive electrodecontaining a positive electrode active material containingLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn), and using a separatorcontaining polyester and satisfying the condition that a pore volumeobtained from a pore size distribution according to a mercury intrusionporosimetry is in a range of 0.9 to 3 cm³/g and an air permeabilityvalue according to a Gurley method (JIS-P-8117) is in a range of 2 to 15sec/100 ml.

In polyester, the thermal stability is excellent since the melting pointis higher than that of polyolefin as one of separator materials, and, inaddition, the amount of water brought into a battery can be reducedsince the hydrophilicity is lower than that of cellulose as one ofseparator materials; therefore, polyester is preferable as a maincomponent of a separator for a nonaqueous electrolyte battery.

Here, it is known that a positive electrode active material representedby Li_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ contains a large amount ofresidual alkali components. When a separator containing polyester isincluded in a nonaqueous electrolyte battery using the positiveelectrode active material, battery resistance that will occur due tohydrolysis in the separator tends to increase.

The major cause of the increase in battery resistance is clogging of theseparator. The clogging of the separator can be avoided by allowing thepore volume, obtained from the pore size distribution according to themercury intrusion porosimetry of the separator, to fall in a range of0.9 to 3 cm³/g. If the pore volume is less than 0.9 cm³/g, there tendsto occur the increase in battery resistance due to the clogging of theseparator resulting from hydrolysis of polyester. On the other hand, ifthe pore volume is more than 3 cm³/g, a satisfactory insulating effectof a positive electrode and a negative electrode according to aseparator is less likely to be obtained. The pore volume is morepreferably in a range of 1 cm³/g to 2 cm³/g. The air permeability valueaccording to the Gurley method (JIS-P-8117) of the separator ispreferably in a range of 2 to 15 sec/100 ml. It is known that the airpermeability value is determined by porosity in a separator, a porediameter of the separator, a thickness of the separator, and tortuosityof the separator that is a ratio of an effective capillary length in theseparator to the separator thickness. Accordingly, the tortuosity valuechanges depending on the change of the air permeability value, in a casethat the porosity, pore diameter, and thickness of the separator are thesame. That is, it is reasonable to assume that, when the airpermeability value is large, the tortuosity value is large and acapillary for ions path in the separator is long and complex. If the airpermeability value is more than 15 sec/100 ml, even when the pore volumeis in a range of 0.9 to 3.0 cm³/g, the increase in battery resistancedue to clogging tends to occur. It is inferred that, if the airpermeability value is more than 15 sec/100 ml, there are small porescausing the increase in battery resistance. The small pores may beeasily clogged. On the other hand, if the air permeability value is lessthan 2 sec/100 ml, a satisfactory insulating effect between a positiveelectrode and a negative electrode by a separator is less likely to beobtained. The air permeability value is more preferably in a range of 3to 10 sec/100 ml.

Accordingly, in the battery of the present embodiment, althoughhydrolysis in the separator due to residual alkali components in thepositive electrode active material represented byLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ occurs, since clogging of theseparator due to the hydrolysis can be reduced, the increase in batteryresistance can be suppressed, and the cycle life performance can beimproved.

Although the separator may be made of polyester, the separatorpreferably contains, other than polyester, at least one kind of polymerselected from the group consisting of cellulose, polyolefin, polyamide,polyimide, and polyvinyl alcohol. This is because when polyester ishydrolyzed, a shape of a separator is easily maintained by the othercomponents, so that the battery performance is less likely to beadversely affected.

When the thickness of the separator is in a range of 3 to 25 μm, theeffect of improving the battery performances including the cycle lifeperformance is more easily obtained.

The nonaqueous electrolyte battery preferably contains at least one kindof moisture adsorbent selected from the group consisting of a molecularsieve, silica gel, and alumina. When such a moisture adsorbent exists ina nonaqueous electrolyte battery, hydrolysis of a separator containingpolyester is less likely to occur. For example, the moisture adsorbentmay be directly arranged in a space in a battery or arranged by beingcontained in an electrode, an electrolyte solution, or a resin componentin a battery.

Instead of the moisture adsorbent, or the moisture adsorbent may becontained in a battery (cell), and a moisture scavenger may be containedin a nonaqueous electrolyte. For example, the moisture scavenger may betrialkyl orthoformates, trialkyl orthoacetates, monoisocyanatecompounds, tetraethylsilicate, tris(trimethylsilyl)phosphate,tris(trimethylsilyl)borate, oxalic acid, citric acid, or toluenesulfonicacid. For example, the moisture scavenger may be arranged by beingcontained in an electrode or an electrolyte solution.

A method of measuring the pore volume in the pore size distributionaccording to the mercury intrusion porosimetry will be described below.

As a measuring apparatus, Shimadzu Autopore 9520 (Autopore 9520 modelmanufactured by Shimadzu Corporation) or an apparatus having equivalentfunctions thereto is used. As a sample, an electrode is cut into a sizeof about 25 mm², and the resultant sample is folded to be placed in ameasurement cell and, thus, to be measured under the conditions of aninitial pressure of 20 kPa and a maximum pressure of 414 Mpa. Theinitial pressure of 20 kPa corresponds to about 3 psia and correspondsto a pressure applied to a sample having a pore diameter of about 60 μm.The maximum pressure of 414 Mpa corresponds to about 59986 psia andcorresponds to a pressure applied to a sample having a pore diameter ofabout 0.003 μm. An average value of three samples is used as ameasurement result. In organizing data, a pore specific surface area iscalculated regarding a pore shape as a cylindrical shape.

The analysis principle of a mercury intrusion porosimetry is based onthe Washburn's equation (B).

D=−4γ cos θ/P  Equation (B)

In the equation, P is a pressure applied, D is a pore diameter, γ is thesurface tension of mercury (480 dyne·cm⁻¹), and θ is the contact anglebetween mercury and the wall surface of the pore: 140°. Since γ and θare constants, the relationship between the applied pressure P and thepore diameter D can be obtained from the Washburn's equation, and thepore diameter and the volume distribution thereof can be derived bymeasuring the mercury intrusion volume at that time. For the specificson the measurement method, principle, and the like, see “Handbook ofMicroparticles”, Genji Jimbo et al, Asakura Publishing Co., Ltd. (1991),“Method for Measurement of Physical Properties of Powders”, SohachiroHayakawa ed., Asakura Publishing Co., Ltd. (1973), and the like.

This measurement is applied to a measurement sample to be describedbelow. Namely, a separator is taken out from a battery and then immersedin ethyl methyl carbonate for 12 hours. During immersion, stirring isperformed, if necessary, to remove Li salt, and then the dried productis used as a measurement sample. The drying temperature is set to fallwithin a range of a room temperature or more and 60° C. or less. Whenthe air permeability value according to the Gurley method (JIS-P-8117)is measured, this sample is used.

The nonaqueous electrolyte battery according to the embodiment will bedescribed in detail.

The nonaqueous electrolyte battery according to the embodiment includesa positive electrode, a negative electrode, a separator disposed betweenthe positive electrode and the negative electrode, a nonaqueouselectrolyte.

The positive electrode may include a positive electrode currentcollector and a positive electrode material layer (positive electrodeactive material-containing layer) provided on one surface or bothsurfaces of the positive electrode current collector.

The positive electrode material layer may contain a positive electrodeactive material. The positive electrode material layer may furthercontain an electric conductive agent and a binder, if necessary.

The positive electrode current collector may include a portion where thepositive electrode material layer is not arranged on a surface. Aportion of the positive electrode current collector, which is notcovered with the positive electrode material layer can serve as apositive electrode tab. Alternatively, the positive electrode mayinclude a positive electrode tab which is separate from the positiveelectrode current collector.

The negative electrode may include a negative electrode currentcollector and a negative electrode material layer (negative electrodeactive material-containing layer) provided on one surface or bothsurfaces of the negative electrode current collector.

The negative electrode material layer may contain a negative electrodeactive material. The negative electrode material layer may furthercontain an electric conductive agent and a binder, if necessary.

The negative electrode current collector may include a portion where thenegative electrode material layer is not arranged on a surface. Thisportion can serve as a negative electrode tab. Alternatively, thenegative electrode may include a negative electrode tab which isseparate from the negative electrode current collector.

The separator is disposed between the positive electrode and thenegative electrode. According to this constitution, the positiveelectrode material layer and the negative electrode material layer canface each other through the separator.

The positive electrode, the negative electrode, and the separator canconstitute an electrode group. The electrode group can have variousstructures. For example, the electrode group can have a stack-typestructure. An electrode group having the stack-type structure can beobtained by, for example, stacking a plurality of positive electrodesand negative electrodes with a separator provided between the positiveelectrode material layer and the negative electrode material layer.Alternatively, the electrode group can have a wound-type structure. Anelectrode group having the wound-type structure can be obtained by, forexample, stacking a separator, a positive electrode, a separator, and anegative electrode in this order to form a laminate and winding thislaminate such that the negative electrode is located outside, forexample.

A nonaqueous electrolyte may be impregnated in such an electrode group.

The nonaqueous electrolyte battery according to the embodiment mayfurther include a positive electrode terminal and a negative electrodeterminal.

A portion of the positive electrode terminal is electrically connectedto a portion of the positive electrode, whereby the positive electrodeterminal can serve as a conductor allowing electrons to move between thepositive electrode and an external circuit. The positive electrodeterminal can be connected to, for example, a positive electrode currentcollector, particularly a positive electrode tab. Similarly, a portionof the negative electrode terminal is electrically connected to aportion of the negative electrode, whereby the negative electrodeterminal can serve as a conductor allowing electrons to move between thenegative electrode and an external terminal. The negative electrodeterminal can be connected to, for example, a negative electrode currentcollector, particularly a negative electrode tab.

The nonaqueous electrolyte battery according to the embodiment mayfurther include a container member. The container member can store theelectrodes and the nonaqueous electrolyte. A portion of each of thepositive electrode terminal and the negative electrode terminal canextend from the container member.

Hereinafter, each member included in the nonaqueous electrolyte batteryaccording to the embodiment will be described.

1) Negative Electrode

As a negative electrode current collector, a metal foil or an alloy foilis used, for example. A thickness of a current collector is preferably20 μm or less and more preferably 15 μm or less. The metal foil may be acopper foil or an aluminum foil. In the case of the aluminum foil, thealuminum foil preferably has a purity of 99% by weight or more. Thealloy foil may be a stainless foil or an aluminum alloy foil. Aluminumalloy in an aluminum alloy foil preferably contains at least one kind ofelement selected from the group consisting of magnesium, zinc, andsilicon. An alloy component preferably contains transition metals suchas iron, copper, nickel, and chromium in an amount of 1% by weight orless.

Examples of a negative electrode active material include carbonaceousmaterials capable of inserting and extracting lithium,titanium-containing oxides, sulfides, lithium nitrides, amorphous tinoxides such as SnB_(0.4)P_(0.6)O_(3.1), tin-silicon oxides such asSnSiO₃, silicon oxides such as SiO, and tungsten oxides such as WO₃. Thecarbonaceous materials may be graphite, hard carbon, soft carbon, orgraphene. One or two or more kinds of negative electrode activematerials may be used.

Although titanium-containing oxides, amorphous tin oxides, tin-siliconoxides, silicon oxides, and tungsten oxides do not contain lithiumbefore charging, lithium can be contained in them by charging.

Examples of titanium-containing oxides include spinel typetitanium-containing oxides, anatase type titanium-containing oxides,rutile type titanium-containing oxides, bronze type titanium-containingoxides, ramsdellite type titanium-containing oxides, orthorhombic typetitanium-containing oxides, monoclinic niobium-titanium-containingoxides, and metal composite oxides containing Ti and at least one kindof element selected from the group consisting of P, V, Sn, Cu, Ni, Nb,and Fe. Examples of the metal composite oxide containing Ti and at leastone kind of element selected from the group consisting of P, V, Sn, Cu,Ni, Nb, and Fe may include TiO₂—P₂O₅, TiO₂—V₂O₅, TiO₂—P₂O₅—SnO₂, andTiO₂—P₂O₅-MeO (Me is at least one kind of element selected from thegroup consisting of Cu, Ni, and Fe). It is preferable that the metalcomposite oxide has low crystallinity and a microstructure in which acrystal phase and an amorphous phase coexist or only an amorphous phaseexists. By adopting such a microstructure, cycling performance can besignificantly improved.

The composition of anatase type, rutile type, or bronze typetitanium-containing oxide can be represented by TiO₂.

The spinel type titanium-containing oxide may be spinel type lithiumtitanium composite oxide. The spinel type lithium titanium compositeoxide may be Li_(4+x)Ti₅O₁₂ (x is changed in a range of 0≦x≦3 bycharge-discharge reaction). The spinel type lithium titanium compositeoxide may be used alone or mixed with other active materials. The othernegative electrode active materials to be mixed may be lithium compoundscapable of allowing lithium or lithium ions to be inserted andextracted. Such lithium compounds include lithium oxides, lithiumsulfides, and lithium nitrides. These compounds include metal compoundswhich contain no lithium in an uncharged state but contain lithium whenthey are charged.

The ramsdellite type titanium-containing oxide may be Li_(2+y)Ti₃O₇ (yis changed in a range of −1≦y≦3 by charge-discharge reaction).

The sulfides may be titanium sulfide such as TiS₂, molybdenum sulfidessuch as MoS₂, or iron sulfides such as FeS, FeS₂, or Li_(x)FeS₂ (0≦x≦2).

The lithium nitrides may be lithium cobalt nitride (for example,Li_(x)Co_(y)N, and here, 0<x<4 and 0<y<0.5).

The orthorhombic type titanium-containing oxides may be a compoundrepresented by a general formulaLi_(2+N)Na_(2−X)M1_(y)Ti_(6−z)M2_(x)O_(14+δ) where M1 is Cs and/or K,and M2 contains at least one of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn,and Al, and 0≦w≦4, 0≦x≦2, 0≦y≦2, 0≦z≦6, and −0.50≦δ≦0.5.

The monoclinic niobium-titanium-containing oxides may be a compoundrepresented by a general formulaLi_(x)Ti_(1−y)M3_(y)Nb_(2−z)M4_(z)O_(7+δ), where M3 is at least oneselected from the group consisting of Zr, Si, Sn, Fe, Co, Mn, and Ni,and M4 is at least one selected from the group consisting of V, Nb, Ta,Mo, W, and Bi, and 0≦x≦5, 0≦y≦1, 0≦z≦2, and −0.3≦δ≦0.3.

Examples of the preferable negative electrode active material includespinel type titanium-containing oxides, anatase type titanium-containingoxides, rutile type titanium-containing oxides, and bronze typetitanium-containing oxides. Furthermore, a negative electrode activematerial containing orthorhombic type titanium-containing oxide and/ormonoclinic niobium-titanium-containing oxide is a preferable material.

The electric conductive agent may be carbon-containing materials such asacetylene black, ketjen black or graphite, or metal powders.

The binder may be polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVdF), fluorine-type rubbers, or styrene butadiene rubber.

It is desirable that a coating weight per unit area of a negativeelectrode material layer is in a range of 10 g/m² or more and 300 g/m²or less. A more preferable range is 20 g/m² or more and 200 g/m² orless.

It is desirable that a density of the negative electrode material layeris in a range of 1.5 g/cm³ or more and 3.2 g/cm³ or less. A morepreferable range is 1.8 g/cm³ or more and 2.5 g/cm³ or less.

The negative electrode can be manufactured by, for example, adding anelectric conductive agent and a binder to a powdery negative electrodeactive material, suspending the negative electrode active material,electric conductive agent, and binder in an appropriate solvent and byapplying this suspension (slurry) to a current collector, followed bydrying and pressing to make a band-shaped electrode.

Concerning the mixing ratio of the negative electrode active material,the electric conductive agent, and the binder on the negative electrodecurrent collector, it is preferable that the negative electrode activematerial is conditioned to an amount of 73 to 98% by weight, theelectric conductive agent is conditioned to an amount of 0 to 20% byweight, and the binder is conditioned to an amount of 2 to 7% by weight.

2) Positive Electrode

A positive electrode active material containsLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn). The positiveelectrode active material may contain only this oxide or may containother kinds of active materials.

The other kinds of active materials include various oxides and sulfides.Examples thereof include manganese dioxide (MnO₂), iron oxide, copperoxide, nickel oxide, lithium-manganese composite oxide (for example,Li_(x)Mn₂O₄ or Li_(x)MnO₂), lithium-nickel composite oxide (for example,Li_(x)NiO₂), lithium-cobalt composite oxide (Li_(x)CoO₂),lithium-nickel-cobalt composite oxide (for example,Li_(x)N_(1−y−z)Co_(y)MzO₂ (M is at least one kind of element selectedfrom the group consisting of Al, Cr, and Fe, 0≦y≦0.5, and 0≦z≦0.1)),lithium-manganese-cobalt composite oxide (for example,Li_(x)Mn_(1−y−z)Co_(y)M_(z)O₂ (M is at least one kind of elementselected from the group consisting of Al, Cr, and Fe, 0≦y≦0.5, and0≦z≦0.1)), lithium-manganese-nickel composite oxide (for example,Li_(x)Mn_(1/2)Ni_(1/2)O₂), spinel type lithium-manganese-nickelcomposite oxide (for example, Li_(x)Mn_(2−y)Ni_(y)O₄), lithiumphosphorus oxides having an olivine structure (such as Li_(x)FePO₄,Li_(x)Fe_(1−y)Mn_(y)PO₄, or Li_(x)CoPO₄), iron sulfate (for example,Fe₂(SO₄)₃), and vanadium oxide (for example, V₂O₅). Also, examples ofthe positive electrode active material include organic materials andinorganic materials such as electroconductive polymer materials, such aspolyaniline or polypyrrole, disulfide type polymer materials, sulfur(S), and carbon fluoride. The above x, y and z whose preferable rangesare not described are preferably in a range of 0 or more and 1 or less.

One or plural kinds of positive electrode active materials may be used.

The electric conductive agent may be carbon black, graphite, graphene,fullerenes, or cokes. Among them, each of carbon black and graphite ispreferred. The carbon black may be acetylene black, ketjen black, orfurnace black.

The binder may be polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVdF), polyacrylic acid, or fluorine-type rubbers.

It is desirable that a positive electrode current collector includes analuminum foil or an aluminum alloy foil.

The average crystal particle size of the aluminum foil or aluminum alloyfoil is preferably 50 μm or less, more preferably 30 μm or less, andstill more preferably 5 μm or less. If the average crystal particle sizeis 50 μm or less, the strength of the aluminum foil or aluminum alloyfoil can be increased, and it is therefore possible to highly densifythe positive electrode under high press pressure, whereby batterycapacity can be increased.

A thickness of a current collector is preferably 20 μm or less and morepreferably 15 μm or less. The purity of the aluminum foil is preferably99% by weight or more. Aluminum alloy is preferably an alloy containingone or more kinds of elements selected from the group consisting ofmagnesium, zinc, and silicon. On the other hand, it is preferable thatthe content of transition metals such as iron, copper, nickel, orchromium is 1% by weight or less.

It is desirable that a coating weight per unit area of a positiveelectrode material layer is in a range of 10 g/m² or more and 300 g/m²or less. A more preferable range is 20 g/m² or more and 220 g/m² orless.

It is desirable that a density of the positive electrode material layeris in a range of 2.0 g/cm³ or more and 4.5 g/cm³ or less. A morepreferable range is 2.8 g/cm³ or more and 4.0 g/cm³ or less.

The positive electrode is manufactured by, for example, adding anelectric conductive agent and a binder to a positive electrode activematerial, suspending the positive electrode active material, electricconductive agent, and binder in an appropriate solvent and by applyingthis suspension to a current collector such as aluminum foil, followedby drying and pressing to make a band-shaped electrode.

Concerning the mixing ratio of the positive electrode active material,the electric conductive agent, and the binder, it is preferable for thepositive electrode active material to be used in an amount of 80 to 95%by weight, for the electric conductive agent to be used in an amount of3 to 20% by weight, and for the binder to be used in an amount of 2 to7% by weight.

3) Nonaqueous Electrolyte

The nonaqueous electrolyte may contain a nonaqueous solvent and anelectrolyte salt to be dissolved in this nonaqueous solvent. Also, apolymer may be contained in the nonaqueous solvent.

The electrolyte salt may be lithium salts such as LiPF₆, LiBF₄,Li(CF₃SO₂)₂N (bistrifluoromethanesulfonylamide lithium (popular name:LiTFSI)), LiCF₃SO₃ (popular name: LiTFS), Li(C₂F₃SO₂)₂N(bispentafluoroethanesulfonylamide lithium (popular name: LiBETI)),LiClO₄, LiAsF₆, LiSbF₆, lithium bis-oxalatoborate (LiB(C₂O₄)₂ (popularname: LiBOB)), difluoro(oxalato) lithium borate (LiF₂BC₂O₄),difluoro(trifluoro-2-oxide-2-trifluoro-methylpropionate(2-)-0,0) lithiumborate (LiBF₂(OCOOC(CF₃)₂) (popular name: LiBF₂(HHIB))), or lithiumdifluorophosphate (LiPO₂F₂). These electrolyte salts may be used eithersingly or in combination of two or more. Particularly, each of LiPF₆,LiBF₄, lithium bis-oxalatoborate (LiB(C₂O₄)₂ (popular name: LiBOB)),difluoro (oxalato) lithium borate (LiF₂BC₂O₄),difluoro(trifluoro-2-oxide-2-trifluoro-methylpropionate(2-)-0,0) lithiumborate (LiBF₂(OCOCC(CF₃)₂) (popular name: LiBF₂(HHIB))), and lithiumdifluorophosphate (LiPO₂F₂) is preferable.

Here, the concentration of the electrolyte salt is preferably in a rangeof 0.5 M or more and 3 M or less. Thus, the performance when supplying ahigh load current can be improved.

The nonaqueous solvent may be, though not particularly limited to,propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane(DME), γ-butyrolactone (GBL), tetrahydrofuran (THF),2-methyltetrahydrofuran (2-MeHF), 1,3-dioxolan, sulfolane, acetonitrile(AN), diethyl carbonate (DEC), dimethyl carbonate (DMC), methylethylcarbonate (MEC), or dipropyl carbonate (DPC). These solvents may be usedeither singly or in combination of two or more. When two or moresolvents are combined, these solvents are all preferably selected fromthose having a dielectric constant of 20 or more.

Additives may be added to this nonaqueous electrolyte. Examples of theseadditives include, though not particularly limited to, vinylenecarbonate (VC), fluorovinylene carbonate, methylvinylene carbonate,fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylenecarbonate, butylvinylene carbonate, dimethylvinylene carbonate,diethylvinylene carbonate, dipropylvinylene carbonate, vinylene acetate(VA), vinylene butylate, vinylene hexanate, vinylene crotonate, catecholcarbonate, propane sultone, and butane sultone. One or two or more kindsof additives may be used.

This nonaqueous electrolyte preferably contains a moisture scavenger.

4) Separator

A separator contains polyester as a material. The separator may be madeof only polyester or a combination of two or more kinds of materialsincluding polyester and materials other than polyester. The materialsother than polyester may be at least one kind of polymers selected fromthe group consisting of polyolefin, cellulose, polyester, polyvinylalcohol, polyamide, polyimide, polytetrafluoroethylene, and vinylon.Among the materials other than polyester, each of cellulose, polyolefin,polyamide, polyimide, and polyvinyl alcohol is preferable.

In the separator, a porous film or nonwoven fabric containing polyestermay be used. The porous film or nonwoven fabric may contain inorganicparticles.

5) Container Member

As a container member, a laminate film having a thickness of 0.5 mm orless or a metal container having a thickness of 3 mm or less is used.The metal container preferably has a thickness of 0.5 mm or less.Alternatively, a resin container may be used. Examples of materials fora resin container include a polyolefin resin, a polyvinyl chlorideresin, a polystyrene resin, an acrylic resin, a phenolic resin, apolyphenylene resin, and a fluorine resin.

The shape of the container member, that is, the battery shape may beflat type (thin type), rectangular type, cylindrical type, coin type,button type, and the like. The battery can be used in either compactapplications in which it is loaded in, for example, portable electronicdevices, or large applications in which it is loaded in vehiclesincluding two-wheel or four-wheel vehicles.

As the laminate film, a multi-layered films including a metal layerbetween resin layers. The metal layer is preferably made from analuminum foil or an aluminum alloy foil, because of weight saving. Theresin layer may be formed using, for example, a polymer material such aspolypropylene (PP), polyethylene (PE), nylone, and polyethyleneterephthalate (PET). The laminate film can be heat-sealed to form intothe shape of the container member.

The metal container is made from aluminum or aluminum alloy. Aluminumalloy preferably contains at least one kind of element selected from thegroup consisting of magnesium, zinc, and silicon and the like. When thealloy includes a transition metal such as iron, copper, nickel, orchromium, the content thereof is preferably controlled to 100 ppm orless.

6) Negative Electrode Terminal

A negative electrode terminal may include aluminum or aluminum alloycontaining at least one kind of element selected from the groupconsisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The negative electrodeterminal is preferably made of the same material as that of the negativeelectrode current collector in order to reduce the contact resistancewith the negative electrode current collector.

7) Positive Electrode Terminal

A positive electrode terminal preferably includes aluminum or aluminumalloy containing at least one kind of element selected from the groupconsisting of Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si. The positiveelectrode terminal is preferably made of the same material as that ofthe positive electrode current collector in order to reduce the contactresistance with the positive electrode current collector.

FIG. 1 shows an example of the nonaqueous electrolyte battery of theembodiment. The battery shown in FIG. 1 is a sealed prismatic nonaqueouselectrolyte battery. The nonaqueous electrolyte battery includes anouter can 1, a lid 2, a positive electrode external terminal 3, anegative electrode external terminal 4, and an electrode group 5. Acontainer member includes the outer can 1 and the lid 2.

The outer can 1 has a bottomed square cylindrical shape and is formedof, for example, metal such as aluminum, aluminum alloy, iron, orstainless steel.

As shown in FIG. 2, a flat-type electrode group 5 is produced by windinga positive electrode 6 and a negative electrode 7 in a flat shape with aseparator 8 being interposed therebetween. The positive electrode 6includes a band-shaped positive electrode current collector made of, forexample, a metal foil, a positive electrode tab 6 a having one endportion parallel to the long side of the positive electrode currentcollector, and a positive electrode material layer (positive electrodeactive material-containing layer) 6 b provided on the positive electrodecurrent collector except for at least the positive electrode tab 6 a. Onthe other hand, the negative electrode 7 includes a band-shaped negativeelectrode current collector made of, for example, a metal foil, anegative electrode tab 7 a having one end portion parallel to the longside of the negative electrode current collector, and a negativeelectrode material layer (negative electrode active material-containinglayer) 7 b provided on the negative electrode current collector exceptfor at least the negative electrode tab 7 a.

The positive electrode 6, the separator 8, and the negative electrode 7are wound with the positive electrode 6 and the negative electrode 7positionally deviated such that the positive electrode tab 6 a projectsfrom the separator 8 in the winding axial direction of the electrodegroup and the negative electrode tab 7 a projects from the separator 8in the opposite direction. According to such winding, in the electrodegroup 5, as shown in FIG. 2, the spirally wound positive electrode tab 6a projects from one end surface, and the spirally wound negativeelectrode tab 7 a projects from the other end surface. An electrolytesolution (not shown) is impregnated in the electrode group 5.

As shown in FIG. 1, the positive electrode tab 6 a and the negativeelectrode tab 7 a are divided into two bundles from the portion near thewinding center of the electrode group. A conductive holding member 9 hassubstantially U-shaped first and second holding portions 9 a and 9 b,and a connecting portion 9 c which electrically connects the firstholding portion 9 a and the second holding portion 9 b. In the positiveand negative electrode tabs 6 a and 7 a, one bundle is held by the firstholding portion 9 a, and the other bundle is held by the second holdingportion 9 b.

The positive electrode lead 10 has a substantially rectangular-shapedsupport plate 10 a, a through hole 10 b which is opened in the supportplate 10 a, and strip-shaped current collecting portions 10 c and 10 dwhich are configured by branching from the support plate 10 a and extenddownward. On the other hand, a negative electrode lead 11 has asubstantially rectangular-shaped support plate 11 a, a through hole 11 bwhich is opened in the support plate 11 a, and strip-shaped currentcollecting portions 11 c and 11 d which are configured by branching fromthe support plate 11 a and extend downward.

The positive electrode lead 10 holds the holding member 9 between thecurrent collecting portions 10 c and 10 d. The current collectingportion 10 c is disposed at the first holding portion 9 a of the holdingmember 9. The current collecting portion 10 d is disposed at the secondholding portion 9 b. The current collecting portions 10 c and 10 d, thefirst and second holding portions 9 a and 9 b, and the positiveelectrode tab 6 a are joined by ultrasonic welding, for example.According to this constitution, the positive electrode 6 of theelectrode group 5 and the positive electrode lead 10 are electricallyconnected through the positive electrode tab 6 a.

The negative electrode lead 11 holds the holding member 9 between thecurrent collecting portions 11 c and 11 d. The current collectingportion 11 c is disposed at the first holding portion 9 a of the holdingmember 9. On the other hand, the current collecting portion 11 d isdisposed at the second holding portion 9 b. The current collectingportions 11 c and 11 d, the first and second holding portions 9 a and 9b, and the negative electrode tab 7 a are joined by ultrasonic welding,for example. According to this constitution, the negative electrode 7 ofthe electrode group 5 and the negative electrode lead 11 areelectrically connected through the negative electrode tab 7 a.

Although the materials of the positive and negative electrode leads 10and 11 and the holding member 9 are not limited particularly, it isdesirable that they are formed of the same material as the positive andnegative electrode external terminals 3 and 4. The positive electrodeexternal terminal 3 is made of, for example, aluminum or aluminum alloy,and the negative electrode external terminal 4 is made of, for example,aluminum, aluminum alloy, copper, nickel, iron plated with nickel, orthe like. For example, when an external terminal is made of aluminum oraluminum alloy, a lead is preferably made of aluminum or aluminum alloy.When the external terminal is made of copper, it is desirable that thelead is made of copper.

The lid 2 having a rectangular plate shape is seamlessly welded to anopening of the outer can 1 by, for example, a laser. The lid 2 is madeof, for example, metal such as aluminum, aluminum alloy, iron, orstainless steel. It is desirable that the lid 2 and the outer can 1 aremade of metal of the same kind. The positive electrode external terminal3 is electrically connected to the support plate 10 a of the positiveelectrode lead 10, and the negative electrode external terminal 4 iselectrically connected to the support plate 11 a of the negativeelectrode lead 11. An insulating gasket 12 is disposed between thepositive electrode external terminal 3 and the lid 2 to electricallyinsulate the positive electrode external terminal 3 and the lid 2. Aninsulating gasket 12 is disposed between the negative electrode externalterminal 4 and the lid 2 to electrically insulate the negative electrodeexternal terminal 4 and the lid 2. It is desirable that the insulatinggasket 12 is a resin-molded product.

According to the above-described nonaqueous electrolyte battery of thefirst embodiment, since the battery includes a positive electrodecontaining Li_(1−x)Ni_(1−a−b−c)Co_(a)Mn_(b)M_(c)O₂ and the separator inwhich the pore volume is in the range of 0.9 to 3 cm³/g and the airpermeability value is in the range of 2 to 15 sec/100 ml and whichcontains polyester, the charge-and-discharge cycle performance can beimproved.

Second Embodiment

According to the second embodiment, a battery pack including anonaqueous electrolyte battery is provided. As the nonaqueouselectrolyte battery, the nonaqueous electrolyte battery according to thefirst embodiment is used. The battery pack may include one or aplurality of nonaqueous electrolyte batteries (unit cells). When thebattery pack includes a plurality of unit cells, the unit cells areelectrically connected in series or parallel.

Such a battery pack will be described in detail with reference to FIG.3. A plurality of unit batteries 21 are electrically connected to eachother in series to constitute a battery module 22. A positive electrodelead 23 is connected to a positive electrode terminal of the batterymodule 22, and its tip is inserted into a positive electrode connector24 to electrically connect it. A negative electrode lead 25 is connectedto a negative electrode terminal of the battery module 22, and its tipis inserted into a negative electrode connector 26 to electricallyconnect it. These connectors 24 and 26 are connected to a protectivecircuit 29 through wirings 27 and 28.

The thermistor 30 detects a temperature of the unit battery 21, and thedetection signal thereof is transmitted to the protective circuit 29.The protective circuit 29 can interrupt a plus wiring 32 a and a minuswiring 32 b between the protective circuit 29 and the terminal 31 fordistributing power to external devices at a predetermined condition. Thepredetermined condition may include, for example, a condition in whichthe detection temperature of the thermistor 30 is a predeterminedtemperature or more. Also, the predetermined condition may include acondition in which over-charge, over-discharge, and overcurrent of theunit battery 21 are detected. Each of the unit batteries 21 or thebattery module is subjected to the detection of the over-charge and thelike. When each of the unit batteries 21 is detected, a battery voltagemay be detected, or a positive electrode potential or a negativeelectrode potential may be detected. In the latter case, a lithiumelectrode used as a reference electrode is inserted into each of theunit batteries 21. In the case of FIG. 3, wirings 33 are connected toeach of the unit batteries 21 for voltage detection, and detectionsignals are transmitted to the protective circuit 29 through thesewirings 33.

In FIG. 3, although an embodiment in which the unit batteries 21 areconnected in series is described, they may be connected in parallel, forincreasing a battery capacity. The battery packs may be connected inseries or in parallel.

The embodiments of the battery pack may be appropriately altereddepending on the application thereof. The battery pack is preferablyused in applications in which cycle characteristics at large current aredesired. Specific examples include power sources for digital cameras,and vehicle-mounted batteries for two- or four-wheel hybrid electricvehicles, two- or four-wheel electric vehicles, and motor-assistedbicycles. Vehicle-mounted batteries are particularly preferred.

According to the battery pack of the second embodiment which has beendetailed above, since the battery pack includes the nonaqueouselectrolyte battery of the first embodiment, a battery pack excellent inthe charge-and-discharge cycle performance can be provided.

EXAMPLES

Hereinafter, although examples will be described, the present inventionis not limited to the following examples as long as not exceeding thegist thereof.

Example A1

<Production of Positive Electrode>

As a positive electrode active material, LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂was provided. As an electric conductive agent, graphite and acetyleneblack were provided. As a binder, polyvinylidene fluoride (PVdF) wasprovided. Next, the positive electrode active material, graphite,acetylene black, and PVdF were mixed to obtain a mixture. In that case,graphite was added in an amount of 2.5% by weight based on the weight ofthe positive electrode material layer. Acetylene black was added in anamount of 2.5% by weight based on the weight of the positive electrodematerial layer. PVdF was added in an amount of 5% by weight based on theweight of the positive electrode material layer. Next, the obtainedmixture was dispersed in an N-methylpyrrolidone (NMP) solvent to preparea slurry. The obtained slurry was coated onto an aluminum foil having athickness of 15 μm such that the coated amount per unit area was 80g/m², and the coating was dried. Subsequently, the dried coating waspressed. Thus, a positive electrode in which the coating weight per unitarea of a positive electrode material layer was 80 g/m² and which had adensity of 3 g/cm³ was produced.

<Production of Negative Electrode>

As a negative electrode active material, spinel type lithium titaniumcomposite oxide Li₄Ti₅O₁₂ was provided. As an electric conductive agent,graphite was provided. As a binder, PVdF was provided. Next, thenegative electrode active material, graphite, and PVdF were mixed toobtain a mixture. In that case, graphite was added in an amount of 3% byweight based on the weight of the negative electrode material layer.PVdF was added in an amount of 2% by weight based on the weight of thenegative electrode material layer. Next, the obtained mixture was mixedin an N-methylpyrrolidone (NMP) solution to prepare a slurry. Theobtained slurry was coated onto a current collector made of an aluminumfoil having a thickness of 15 μm such that the coated amount per unitarea was 120 g/m², and the coating was dried. Subsequently, the driedcoating was pressed to form a negative electrode material layer on thecurrent collector. Thus, a band-shaped negative electrode in which thecoating weight per unit area of a negative electrode material layer was120 g/m² and which had a density of 2.1 g/cm³ was produced.

<Preparation of Nonaqueous Electrolyte>

1M concentration of LiPF₆ was mixed and dissolved in a nonaqueoussolvent containing 33% by volume of ethylene carbonate (EC) and 67% byvolume of diethyl carbonate (DEC) to prepare a nonaqueous electrolytesolution as a nonaqueous electrolyte.

<Assembly of Battery>

A separator made of a polyester nonwoven fabric having a thickness of 20μm was provided. When the pore volume of that separator in a pore sizedistribution analysis according to a mercury intrusion porosimetry wasobtained by the above-described method, the pore volume was 1.5 cm³/g,and the air permeability value according to the Gurley method(JIS-P-8117) was 8 sec/100 ml.

The previously prepared nonaqueous electrolyte was immersed in thisseparator. Subsequently, the previously produced positive electrode wascovered with this separator, and then the previously produced negativeelectrode was staked to face the positive electrode through theseparator, whereby a laminate was obtained. The laminate was woundspirally to produce a spiral-shaped electrode group. The electrode groupwas pressed to be formed into a flat shape.

The flat-shaped electrode group was inserted into a bottomed rectangularcylindrical can made of aluminum having a thickness of 0.3 mm, and thecan was sealed with a lid member. Thus, a flat-type nonaqueouselectrolyte secondary battery having a thickness of 5 mm, a width of 30mm, a height of 25 mm, and a weight of 100 g was manufactured.

Examples A2 to A12 and B1 to B9 and Comparative Examples A1 to 4 and B1to B9

Secondary batteries similar to Example Al were manufactured except thatthe materials, thicknesses, pore volumes in the pore size distributionanalysis according to the mercury intrusion porosimetry, and airpermeabilities according to the Gurley method of separators, electrolytesolution compositions, presence of a moisture adsorbent in thebatteries, and compositions of positive electrodes shown in Tables 1 to4 were used.

Examples B10 to B17 and Comparative Examples B10 to B17

Secondary batteries similar to Example Al were manufactured except thatthe materials, thicknesses, pore volumes in the pore size distributionanalysis according to the mercury intrusion porosimetry, and airpermeabilities according to the Gurley method of separators, electrolytesolution compositions, presence of a moisture adsorbent in thebatteries, compositions of positive electrodes, and compositions ofnegative electrodes shown in Tables 5 to 8 were used.

Each moisture adsorbent in Examples A-7 to A-9 was arranged in a cell bythe following method. Powders of a molecular sieve, silica gel, andalumina as moisture adsorbents were subjected to vacuum drying at 200°C. to remove moisture. 2 wt % of the moisture adsorbent from which themoisture was removed was added to an electrolyte solution in a glove boxin which the dew point was managed such that the dew point was less thanminus 60° C., and the resultant electrolyte solution mixed with themoisture adsorbent was injected into a cell to dispose the moistureadsorbent in the cell.

The obtained secondary battery was brought into a state in which a depthof discharge (DOD) was 50%, subjected to resistance measurement under anenvironment of 25° C., then stood under an environment of 70° C. for 30days, and subsequently subjected to resistance measurement under anenvironment of 25° C. to measure the resistance increase rate. Themeasurement results are shown in Tables 2 and 4.

FIG. 4 shows the pore size distribution in Example A-1 and ComparativeExample A-1. In FIG. 4, the horizontal axis represents the pore size(w)), and the vertical axis represents the pore volume (cm³g).

As seen in FIG. 4, in the separator used in the battery of Example A-1,the volume of pores having a pore size of 1 μm or less is larger thanthat in Comparative Example A-1.

TABLE 1 Positive electrode Negative electrode Coating Coating Separatorweight per Den- weight per Den- Thick- Pore Air per- Active unit areasity Active unit area sity ness volume meability Material g/m² g/cm³Material g/m² g/cm³ Material μm cm²/g sec/100 ml ExampleA-1LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8ExampleA-2 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester20 0.9 8 ExampleA-3 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 3 8 ExampleA-4 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂120 2.1 Polyester 20 1.5 2 ExampleA-5 LiNi_(0.5)Co_(2.2)Mn_(0.3)O₂ 80 3Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 15 ExampleA-6LiNi_(0.5)Co_(3.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8ExampleA-7 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester20 1.5 8 ExampleA-8 LiNi_(0.8)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleA-9 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8 ExampleA-10LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Nonwoven fabric of20 1.5 8 mixture of polyester and cellulose (67:33)(weight ratio)ExampleA-11 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Nonwovenfabric of 20 1.5 8 mixture of polyester and polyethylene (67:33)(weightratio) ExampleA-12 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Nonwoven fabric of 20 1.5 8 mixture of polyester and polypropylene(67:33)(weight ratio) ExampleB-1 LiNi_(0.2)Co_(0.52)Mn_(0.53)O₂ 80 3Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8 ExampleB-2LiNi_(0.6)Co_(6.2)Mn_(0.2)O₂ 75 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8ExampleB-3 LiNi_(2.7)Co_(0.15)Mn_(0.15)O₂ 70 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-4 LiNi_(8.8)Co_(0.1)Mn_(0.1)O₂ 70 3Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8 ExampleB-5LiNi_(0.5)Co_(0.2)Mn_(0.2)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8ExampleB-6 LiNi_(0.53)Co_(0.1)Al_(0.05)O₂ 70 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-7 LiNi_(0.5)Co_(0.15)Al_(0.05)O₂ 70 3Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8 ExampleB-8LiNi_(0.8)Co_(0.2)Mn_(0.3)O₂ 85 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.5 8and LiCoO₂(67:33) (weight ratio) ExampleB-9LiNi_(0.33)Co_(0.33)Mn_(0.33)O₂ 85 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 1.58 and LiCoO₂(67:33) (weight ratio)

TABLE 2 Resistance Moisture increase Electrolyte solution compositionadsorbent rate (%) ExampleA-1 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volumeratio) ExampleA-2 1 mol-LiPF₆/EC:DEC(33:67) non 30 (volume ratio)ExampleA-3 1 mol-LiPF₆/EC:DEC(33:67) non 20 (volume ratio) ExampleA-4 1mol-LiPF₆/EC:DEC(33:67) non 20 (volume ratio) ExampleA-5 1mol-LiPF₆/EC:DEC(33:67) non 20 (volume ratio) ExampleA-6 1mol-LiPF₆/EC:DEC(33:67) non 5 (volume ratio) and 1 wt%-tris(trimethyl)phosphate ExampleA-7 1 mol-LiPF₆/EC:DEC(33:67)Molecular 5 (volume ratio) sieve ExampleA-8 1 mol-LiPF₆/EC:DEC(33:67)Silica gel 5 (volume ratio) ExampleA-9 1 mol-LiPF₆/EC:DEC(33:67) Alumina5 (volume ratio) ExampleA-10 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volumeratio) ExampleA-11 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio)ExampleA-12 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-1 1mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-2 1mol-LiPF₆/EC:DEC(33:67) non 15 (volume ratio) ExampleB-3 1mol-LiPF₆/EC:DEC(33:67) non 15 (volume ratio) ExampleB-4 1mol-LiPF₆/EC:DEC(33:67) non 15 (volume ratio) ExampleB-5 1mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-6 1mol-LiPF₆/EC:DEC(33:67) non 20 (volume ratio) ExampleB-7 1mol-LiPF₆/EC:DEC(33:67) non 20 (volume ratio) ExampleB-8 1mol-LiPF₆/EC:DEC(33:67) non 15 (volume ratio) ExampleB-9 1mol-LiPF₆/EC:DEC(33:67) non 15 (volume ratio)

TABLE 3 Positive electrode Negative electrode Coating Coating Separatorweight per weight per Pore Air Active unit area Density Active unit areaDensity Thickness volume permeability material g/m² g/cm³ material g/m²g/cm³ Material μm cm³/g sec/100 ml ComparativeLiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 0.8 8ExampleA-1 Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 3.2 8 ExampleA-2 ComparativeLiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyaster 20 1.5 1ExampleA-3 Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 1.5 20 ExampleA-4 ComparativeLiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 0.8 8ExampleB-1 Comparative LiNi_(0.8)Co_(0.2)Mn_(0.2)O₂ 75 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 0.8 8 ExampleB-2 ComparativeLiNi_(0.7)Co_(0.16)Mn_(0.15)O₂ 70 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 0.8 8ExampleB-3 Comparative LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ 70 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 0.8 8 ExampleB-4 ComparativeLiNi_(0.5)Co_(0.3)Mn_(0.2)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 0.8 8ExampleB-5 Comparative LiNi_(0.88)Co_(0.1)Al_(0.05)O₂ 70 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 0.8 8 ExampleB-6 ComparativeLiNi_(0.8)Co_(0.15)Al_(0.05)O₂ 70 3 Li₄Ti₅O₁₂ 120 2.1 Polyester 20 0.8 8ExampleB-7 Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 85 3 Li₄Ti₅O₁₂ 1202.1 Polyester 20 0.8 8 ExampleB-8 and LiCoO₂(67:33) (weight ratio)Comparative LiNi_(0.33)Co_(0.33)Mn_(0.33)O₂ 85 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-8 and LiCoO₂(67:33) (weight ratio)

TABLE 4 Resistance Moisture increase Electrolyte solution compositionadsorbent rate (%) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleA-1 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) nonShort ExampleA-2 (volume ratio) circuit Comparative 1mol-LiPF₆/EC:DEC(33:67) non Short ExampleA-3 (volume ratio) circuitComparative 1 mol-LiPF₆/EC:DEC(33:67) non 70 ExampleA-4 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60 ExampleB-1 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 80 ExampleB-2 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 80 ExampleB-3 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 80 ExampleB-4 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60 ExampleB-5 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 90 ExampleB-6 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 90 ExampleB-7 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 70 ExampleB-8 (volume ratio)Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 70 ExampleB-9 (volume ratio)

TABLE 5 Positive electrode Negative electrode Coating Coating Separatorweight per Den- weight per Den- Thick- Pore Air per- Active unit areasity Active unit area sity ness volume meability Material g/m² g/cm³Material g/m² g/cm³ Material μm cm³/g sec/100 ml ExampleB-10Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Mg_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-11Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Si_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-12Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Ti_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-13Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Zn_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-14Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Zr_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 1.5 8 ExampleB-15 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 TiO₂100 2.1 Polyester 20 1.5 8 (bronze type) ExampleB-16LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Nb₂TiO₁ 60 2.6 Polyester 20 1.5 8ExampleB-17 LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Li₂Na₂Ti₈NbO₁₄ 60 2.6Polyester 20 1.5 8

TABLE 6 Resistance Moisture increase Electrolyte solution compositionadsorbent rate (%) ExampleB-10 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volumeratio) ExampleB-11 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio)ExampleB-12 1 mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-131 mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-14 1mol-LiPF₆/EC:DEC(33:67) non 10 (volume ratio) ExampleB-15 1mol-LiPF₆/EC:DEC(33:67) non 30 (volume ratio) ExampleB-16 1mol-LiPF₆/EC:DEC(33:67) non 40 (volume ratio) ExampleB-17 1mol-LiPF₆/EC:DEC(33:67) non 40 (volume ratio)

TABLE 7 Positive electrode Negative electrode Coating Coating Separatorweight per Den- weight per Den- Thick- Pore Air per- Active unit areasity Active unit area sity ness volume meability Material g/m² g/cm³Material g/m² g/cm³ Material μm cm³/g sec/100 ml ComparativeLi(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Mg_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-10 ComparativeLi(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Si_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-11 ComparativeLi(Ni_(0.5)Co_(0.2)Mn_(0.2))_(0.95)Ti_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-12 ComparativeLi(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Zn_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-13 ComparativeLi(Ni_(0.5)Co_(0.2)Mn_(0.3))_(0.95)Zr_(0.05)O₂ 80 3 Li₄Ti₅O₁₂ 120 2.1Polyester 20 0.8 8 ExampleB-14 Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂80 3 TiO₂ 100 2.3 Polyester 20 0.8 8 ExampleB-15 (bronze type)Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3 Ni₂TiO₇ 60 2.6 Polyester20 0.8 8 ExampleB-16 Comparative LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ 80 3Li₂Na₂Ti₅NbO₁₄ 60 2.6 Polyester 20 0.8 8 ExampleB-17

TABLE 8 Resistance Moisture increase Electrolyte solution compositionadsorbent rate (%) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleB-10 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleB-11 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleB-12 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleB-13 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 60ExampleB-14 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 90ExampleB-15 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 80ExampleB-16 (volume ratio) Comparative 1 mol-LiPF₆/EC:DEC(33:67) non 70ExampleB-17 (volume ratio)

By comparing Examples A-1 to A-3 and Comparative Examples A-1 and A-2,when the air permeability value was a constant value in a range of 2sec/100 ml or more and 15 sec/100 ml or less, according to Examples A-1to A-3 in which the pore volume was 0.9 cm³/g or more and 3 cm³/g orless, it was found that the resistance increase rate after hightemperature storage was lower than that in Comparative Example A-1 inwhich the pore volume was less than 0.9 cm³/g. In Comparative ExampleA-2 in which the pore volume is more than 3 cm³/g, internal shortcircuit occurs due to high temperature storage.

By comparing Examples A-1 and A-4 to A-5 and Comparative Examples A-3and A-4, when the pore volume was a constant value in a range of 0.9cm³/g or more and 3 cm³/g or less, according to Examples A-1 and A-4 toA-5 in which the air permeability value was 2 sec/100 ml or more and 15sec/100 ml or less, it was found that the resistance increase rate afterhigh temperature storage was lower than that in Comparative Example A-4in which the air permeability value was more than 15 sec/100 ml. InComparative Example A-3 in which the air permeability value is less than2 sec/100 ml, internal short circuit occurs due to high temperaturestorage.

The results of Examples A-6 to A-12 and B-1 to B-9 showed that if anonaqueous electrolyte contained trimethyl phosphate or if a moistureadsorbent was used, the resistance increase rate after high temperaturestorage could be further reduced. The results further showed that if aseparator containing materials other than polyester was used or if apositive electrode active material had a different composition, theresistance increase rate after high temperature storage could bereduced.

The results of Comparative Examples B-1 to B-9 showed that when the porevolume fell outside the range of 0.9 cm³/g or more and 3 cm³/g or less,even if the air permeability value was in the range of 2 sec/100 ml ormore and 15 sec/100 ml or less, the resistance increase rate after hightemperature storage increased.

The results of Examples B-10 to B-14 also showed that when the positiveelectrode active material had a different composition, the resistanceincrease rate after high temperature storage could be reduced. Theresults of B-15 to B-17 showed that when a negative electrode activematerial was different, the resistance increase rate after hightemperature storage could be reduced.

By comparing Examples B-10 to B-17 and Comparative Examples B-10 toB-17, it was confirmed that in Comparative Examples B-10 to B-17 inwhich the pore volume fell outside the range of 0.9 cm³/g or more and 3cm³/g or less, even if the air permeability value was in the range of 2sec/100 ml or more and 15 sec/100 ml or less, the resistance increaserate after high temperature storage was higher than that in ExamplesB-10 to B-17.

According to the above-described nonaqueous electrolyte battery of atleast one embodiment and example, since the battery includes thepositive electrode containing Li_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ andthe separator in which the pore volume is in the range of 0.9 cm³/g ormore and 3 cm³/g or less and the air permeability value is in the rangeof 2 sec/100 ml or more and 15 sec/100 ml or less and which containspolyester, the resistance increase after high temperature storage can bereduced, and a long life can be achieved even under a high temperatureenvironment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed:
 1. A nonaqueous electrolyte battery comprising: apositive electrode comprising a positive electrode active materialcontaining Li_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4,0≦b≦0.45, 0≦c≦0.1, and M represents at least one element selected fromthe group consisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn); a negativeelectrode; a separator, disposed between the positive electrode and thenegative electrode, comprising polyester, in which a pore volume in apore size distribution according to a mercury intrusion porosimetry isin a range of 0.9 cm³/g to 3 cm³/g, and an air permeability valueaccording to a Gurley method is in a range of 2 sec/100 ml to 15 sec/100ml; and a nonaqueous electrolyte.
 2. The nonaqueous electrolyte batteryaccording to claim 1, wherein the separator contains at least one kindof polymer selected from the group consisting of cellulose, polyolefin,polyamide, polyimide, and polyvinyl alcohol.
 3. The nonaqueouselectrolyte battery according to claim 2, wherein a thickness of theseparator is in a range of 3 μm to 25 μm.
 4. The nonaqueous electrolytebattery according to claim 2 further comprising at least one kind ofmoisture adsorbent selected from the group consisting of a molecularsieve, silica gel, and alumina.
 5. The nonaqueous electrolyte batteryaccording to claim 2, wherein the nonaqueous electrolyte comprises amoisture scavenger.
 6. The nonaqueous electrolyte battery according toclaim 2, wherein the negative electrode comprises at least one kind ofnegative electrode active material selected from the group consisting ofspinel type titanium-containing oxide, anatase type titanium-containingoxide, rutile type titanium-containing oxide, and bronze typetitanium-containing oxide.
 7. The nonaqueous electrolyte batteryaccording to claim 2, wherein the negative electrode comprises at leastone kind of negative electrode active material selected from the groupconsisting of spinel type titanium-containing oxide, anatase typetitanium-containing oxide, rutile type titanium-containing oxide, bronzetype titanium-containing oxide, orthorhombic type titanium-containingoxide, and monoclinic niobium-titanium-containing oxide.
 8. A batterypack comprising: a terminal to be connected to an external device; andat least one nonaqueous electrolyte battery, wherein, the nonaqueouselectrolyte battery comprises, a positive electrode comprising apositive electrode active material containingLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn); a negative electrode;a separator, disposed between the positive electrode and the negativeelectrode, comprising polyester, in which a pore volume in a pore sizedistribution according to a mercury intrusion porosimetry is in a rangeof 0.9 cm³/g to 3 cm³/g, and an air permeability value according to aGurley method is in a range of 2 sec/100 ml to 15 sec/100 ml; and anonaqueous electrolyte.
 9. A positive electrode for a battery to be usedwith a negative electrode and a separator, comprising: a currentcollector; and a positive electrode active material containingLi_(x)Ni_(1−a−b)Co_(a)Mn_(b)M_(c)O₂ (0.9<x≦1.25, 0<a≦0.4, 0≦b≦0.45,0≦c≦0.1, and M represents at least one element selected from the groupconsisting of Mg, Al, Si, Ti, Zn, Zr, Ca, and Sn).
 10. The positiveelectrode according to claim 9, wherein the separator comprisespolyester, in which a pore volume in a pore size distribution accordingto a mercury intrusion porosimetry is in a range of 0.9 cm³/g to 3cm³/g, and an air permeability value according to a Gurley method is ina range of 2 sec/100 ml to 15 sec/100 ml.